plloop — Python-like Lua Object-Oriented Programming system

plloop module provides a naive Lua OOP implementation that mimics Python OOP system. It implements automatic bound methods (forget about colon syntactic sugar), __init__ method for new instance initializing, all metatable 'magic' (event) metamethods (e.g. __tostring, __len, __call, __add), multilevel (but not multiple) inheritance, and more.

How to use it

#!/usr/bin/lua

PLLOOP_GLOBAL = true    -- export all module functions to global scope
-- it's possible to specify exported functions:
-- PLLOOP_GLOBAL = {'class', 'instance_of', 'subclass_of'}

local plloop = require('plloop')
-- any function is always acceptable as plloop.function

local CurrySum = class('CurrySum', {

    -- def __init__(self, ...)
    __init__ = function(self, initial_value)
        self.value = self._convert_to_number(initial_value)
    end,

    -- def __str__(self)
    __tostring = function(self)
        return ('<%s obj: %s>'):format(self.__class__.__name__, self.value)
    end,

    -- def __call__(self, ...)
    __call = function(self, plus_value)
        self.value = self.value + self._convert_to_number(plus_value)
        return self
    end,

    -- def __add__(self, other)
    __add = function(self, other)
        return self.value + self._convert_to_number(other)
    end,

    get_value = function(self)
        return self.value
    end,

    set_value = function(self, value)
        self.value = self._convert_to_number(value)
    end,

    -- helper method
    _convert_to_number = function(self, raw)
        if type(raw) == 'table' and raw.__class__ == self.__class__ then
            raw = raw.value
        end
        return tonumber(raw) or 0
    end

})


print(CurrySum)    -- <CurrySum>

local sum1 = CurrySum(7)
print(sum1)    -- <CurrySum obj: 7>

sum1(3)('1')(nil)(10)
print(sum1)    -- <CurrySum obj: 21> (7+3+1+0+10)

local sum2 = CurrySum(23)
print(sum2)    -- <CurrySum obj: 23>

print(sum1 + sum2)    -- 44 (21+23)
print(sum1 + 5)    --- 26 (21+5)
print(sum2 + nil)    --- 23 (23+0)

local sum3 = CurrySum(sum2)
print(sum3)    -- <MyClass obj: 23>

sum3.set_value('43')
print(sum3.get_value())    -- 43
print(CurrySum.get_value(sum3))    -- 43
local bound_method = sum3.get_value
print(bound_method())    -- 43

print(sum1.__id__, sum2.__id__, sum3.__id__)    -- 0x928bb0    0x929e20    0x92a260
print(sum1.__class__, sum1.__class__.__name__)    --- <CurrySum>    CurrySum


local subclass_attrs = {

    -- overloaded method
    __tostring = function(self)
        return ('[%s obj: %s]'):format(self.__class__.__name__, self.value)
    end,

    -- additional method
    get_double_value = function(self)
        return self.value * 2
    end

}

-- Lua 5.3
local SubCurrySum = class('SubCurrySum', subclass_attrs) << CurrySum

-- all supported Lua versions
local SubCurrySum = class('SubCurrySum', subclass_attrs, CurrySum)


print(SubCurrySum)    -- <SubCurrySum>

local subsum = SubCurrySum(9)
print(subsum)    -- [SubCurrySum obj: 9]

print(subsum.get_value())    -- 9

subsum(8)({})(true)(12)('15')
print(subsum.get_value())    -- 44 (9+8+0+0+12+15)

print(subsum.get_double_value())    -- 88


print(is_object(subsum))    -- true
print(instance_of(subsum, SubCurrySum))    -- true
print(instance_of(subsum, CurrySum))    -- true
print(instance_of(subsum, CurrySum, true))    -- false (third arg - direct_only)
print(plloop.is_class(SubCurrySum))    -- true
print(plloop.subclass_of(SubCurrySum, CurrySum))    -- true

How to test it

$ ./run_tests.sh

This script tests plloop with Lua 5.1, 5.2, and 5.3 (you need luaunit module somewhere in package.path).

Where is the documentation?

There is no documentation at the moment. Read plloop.lua and plloop_tests.lua.